A New Model for the Etching Characteristics of Corners Formed by Si{111} Planes on Si{110} Wafer Surface


The etching characteristics of concave and convex corners formed in a microstructure by the intersection of {111} planes in wet anisotropic etchant are exactly opposite to each other. The convex corners are severely attacked by anisotropic Fetchant, while the concave corners remain unaffected. In this paper, we present a new model which explains the root cause of the initiation and advancement of undercutting phenomenon at convex corners and its absence at concave corners on {110} silicon wafers. This contrary etching characteristics of convex and concave corners is explained by utilizing the role of dangling bond in etching process and the etching behavior of the tangent plane at the convex corner. The silicon atoms at the convex edge/ridge belong to a high etch rate tangent plane as compared to {111} sidewalls, which leads to the initiation of undercutting at the convex corner. On the other hand, all the bonds of silicon atoms pertaining to concave edges/ridge are engaged with neighboring atoms and consequently contain no dangling bond, thus resulting in no-undercutting at concave edges/corners.

Share and Cite:

P. Pal and S. Singh, "A New Model for the Etching Characteristics of Corners Formed by Si{111} Planes on Si{110} Wafer Surface," Engineering, Vol. 5 No. 11A, 2013, pp. 1-8. doi: 10.4236/eng.2013.511A001.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] S. Lee, S. Park and D. Cho, “The Surface/Bulk Micromachining (SBM) Process: A New Method for Fabricating Released Microelectromechanical Systems in Single Crystal Silicon,” Journal of Microelectromechanical Systems, Vol. 8, No. 4, 1999, pp. 409-416.
[2] B. Tang and K. Sato, “Formation of Silicon Nano Tips in Surfactant-Modified Wet Anisotropic Etching,” Applied Physics Express, Vol. 4, 2011, Article ID: 056501.
[3] P. Pal and K. Sato, “Complex Three Dimensional Structures in Si{100} Using Wet Bulk Micromachining,” Journal of Micromechanics and Microengineering, Vol. 19, No. 10, 2009, Article ID: 105008.
[4] I. Zubel and M. Kramkowska, “Possibilities of Extension of 3D Shapes by Bulk Micromachining of Different Si (h k l) Substrates,” Journal of Micromechanics and Microengineering, Vol. 15, No. 3, 2005, pp. 485-493.
[5] J. Frühauf, “Shape and Functional Elements of the Bulk Silicon Microtechnique: A Manual of Wet-Etched Silicon Structures,” Springer, 2005.
[6] J. Haneveld, H. Jansen, E. Berenschot, N. Tas and M. Elwenspoek, “Wet Anisotropic Etching for Fluidic 1D Nanochannels,” Journal of Micromechanics and Microengineering, Vol. 13, 2003, pp. S62-S66.
[7] E. S. Kalesar and M. W. Carver, “Deep Anisotropic Etching of Tapered Channels in (110)-Oriented Silicon,” Chemistry of Materials, Vol. 1, No. 6, 1989, pp. 634-639.
[8] A. Lipson and E. M. Yeatman, “A 1-D Photonic Band Gap Tunable Optical Filter in (110) Silicon,” Journal of Microelectromechanical Systems, Vol. 16, No. 3, 2007, pp. 521-527.
[9] A. Holke and H. T. Henderson, “Ultra-Deep Anisotropic Etching of (110) Silicon,” Journal of Micromechanics and Microengineering, Vol. 9, No. 1, 1999, pp. 51-57.
[10] D. L. Kendall, “Vertical Etching of Silicon at Very High Aspect Ratios,” Annual Review of Materials Science, Vol. 9, 1979, pp. 373-403.
[11] P. Pal, K. Sato and S. Chandra, “Fabrication Techniques of Convex Corners in a (100)-Silicon Wafer Using Bulk Micromachining: A Review,” Journal of Micromechanics and Microengineering, Vol. 17, No. 10, 2007, pp. R111R133. http://dx.doi.org/10.1088/0960-1317/17/10/R01
[12] H. K. Trieu and W. Mokwa, “A Generalized Model Describing Corner Undercutting by the Experimental Analysis of TMAH/IPA,” Journal of Micromechanics and Microengineering, Vol. 8, No. 2, 1998, pp. 80-83.
[13] M. Chahoud, H. H. Wehmann and A. Schlachetzki, “Etching Simulation of Convex and Mixed InP and Si Structures,” Sensors and Actuators A, Vol. 69, 1998, pp. 251-258.
[14] H. Schroder and E. Obermeier, “A New Model for Si{100} Convex Corner Undercutting in Anisotropic KOH Etching,” Journal of Micromechanics and Microengineering, Vol. 10, No. 1, 2000, pp. 163-170.
[15] M. Shikida, K. Nanbara, T. Koizumi, H. Sasaki, K. Sato, M. Odagaki, M. Ando, S. Furuta and K. Asaumi, “A Model Explaining Mask-Corner Undercut Phenomena in Anisotropic Silicon Etching: A Saddle Point in the Etching-Rate Diagram,” Sensors and Actuators A, Vol. 97-98, 2000, pp. 758-763.
[16] W. T. Chang Chien, C. O. Chang, Y. C. Lo, Z. W. Li and C. S. Chou, “On the Miller-Indices Determination of Si{100} Convex Corner Undercut Planes,” Journal of Micromechanics and Microengineering, Vol. 15, No. 4, 2005, pp. 833-842.
[17] C. Jia, W. Dong, C. Liu, X. Zhang, J. Zhou, Z. Zhong, H. Xue, H. Zang, B. Xu and W. Chen, “Convex Corners Undercutting and Rhombus Compensation in KOH with and without IPA Solution on (110) Silicon,” Microelectronics Journal, Vol. 37, No. 11, 2006, pp. 1297-1301.
[18] B. Kim and D. D. Cho, “Aqueous KOH Etching of Silicon (110) Etch Characteristics and Compensation Methods for Convex Corners,” Journal of The Electrochemical Society, Vol. 145, No. 7, 1998, pp. 2499-2508.
[19] W. Dong, X. Zhang, C. Liu, M. Li, B. Xu and W. Chen, “Mechanism for Convex Corner Undercutting of (110) Silicon in KOH,” Microelectronics Journal, Vol. 35, No. 5, 2004, pp. 417-419.
[20] D. R. Ciarlo, “Corner Compensation Structures for (110)Oriented Silicon,” Proceedings of the IEEE MicroRobots and Teleoperators Workshop, Hyannis, 1987.
[21] M. Shikida, K. Sato, K. Tokoro and D. Uchikawa, “Differences in Anisotropic Etching Properties of KOH and TMAH Solutions,” Sensors and Actuators A, Vol. 80, No. 2, 2000, pp. 179-188.
[22] H. Seidel, L. Csepregi, A. Heuberger and H. Baumgartel, “Anisotropic Etching of Crystaline Silicon in Alkaline Solutions,” Journal of the Electrochemical Society, Vol. 137, No. 11, 1990, pp. 3613-3631.
[23] R. J. Jaccodine, “Use of Modified Free Energy Theorems to Predict Equilibrium Growing and Etching Shapes,” Journal of Applied Physics, Vol. 33, No. 8, 1962, pp. 2643-2647. http://dx.doi.org/10.1063/1.1729036
[24] P. Pal, M. A. Gosalvez and K. Sato, “Silicon Micromachining Based on Surfactant-Added Tetramethyl Ammonium Hydroxide: Etching Mechanism and Advanced Application,” Japanese Journal of Applied Physics, Vol. 49, 2010, Article ID: 056702.

Copyright © 2023 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.